1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same.
2. Description of Related Art
As semiconductor device integration increases, a size of an active region on which a channel is formed is reduced. Semiconductor devices having small active regions may exhibit high leakage currents and low driving performances. For example, when a channel length is reduced, a short channel effect can occur, and when a channel width is reduced, a driving current can be decreased.
Accordingly, there is a need to increase a channel area in highly integrated semiconductor devices. For example, the active region can have a larger surface area by forming a protrusion in the active region with respect to an isolation layer. In the active region, sidewalls as well as an upper surface can be used as a channel, and thus, the driving performance of the semiconductor device can be increased.
When the sidewalls of an active region are used as a channel, an electric field can be enhanced in an edge portion of the active region. The electric field increases as the curvature radius of the edge portion of the active region decreases. A threshold voltage of a semiconductor device can be changed according to the profile of the edge portion of the active region, and the threshold voltages between semiconductor devices respectively fabricated using a single wafer or a single batch have a wide distribution range. The wide distribution range of the threshold voltages decreases the reliability of the semiconductor device.
Furthermore, the profile of the edge portion of the active region can affect the programming characteristics of a non-volatile memory device. When the electric field is enhanced in the edge portion of the active region, more tunneling effects of electrons or holes may occur in the edge portion of the active region. As a result, a tunneling insulating layer disposed on the edge portion of the active region deteriorates, and the non-volatile memory device has low durability and low high-temperature reliability.